1. Field of the Invention
The invention relates to apparatus for pumping oil wells, and, more particularly, to gas release apparatus for oil well pumps.
2. Description of the Prior Art
Production of oil from oil wells is usually accompanied by some of the gas in the well flowing through the down hole pumps. If this gas is allowed to accumulate in the barrel of the downhole pump, a condition known as "gas lock" occurs. Such a condition occurs when foamy oil or surges of subterranean gases become trapped between the plunger of the traveling-plunger-type downhole pump and the standing valve at the bottom of the pump. In such a condition, little if any fluid can be pumped out of the well. The downhole pump may simply be compressing and expanding the gas that is locked in the barrel. The forces of the huydrostatic or column of fluid, when the column is generally several feet in height, bearing on the plunger, causes the trapped gases to compress and decompress. This keeps the plunger and the standing valve closed preventing the pump from working.
The nature of valves used in existing downhole oil well pumps lends itself to the creation of gas locks. Normally, the pressure differential across the traveling ball valve of the plunger during the downward stroke opens the valve and allows the fluid in the pump barrel to escape into the discharge tubing. If the fluid in the pump barrel is mostly gas, the traveling ball valve may not open. Thus, as heretofore stated, the pump will not be operating properly and little if any fluid will be flowing into the discharge tubing.
In the past, it has been suggested to remedy such condition by preventing gas from reaching the pump. This was accomplished by using an annulus below the pump inlet. However, in order to implement such a remedy, accurate data is required about the generally unknown formation characteristics. Furthermore, the fluid reservoir characteristics of such formations change with time, requiring constant adjustments to the pump installations. Therefore, the annulus method of preventing gas from reaching the pump is neither practical or effective.
In U.S. Pat. No. 1,676,186 to Hawkins, a valve control for plunger-type pumps is disclosed. However, this arrangement depends on precise spacing of the internal parts which is quite impractical. In U.S. Pat. No. 1,067,312 to Conrader, a pump is disclosed for pumping gas. Again, spacing is quite critical and no provision is made to prevent gas lock. Also, such apparatus cannot positively pump on each cycle. In U.S. Pat. No. 1,793,572 to Von Linde, a tubing check valve for a pump is disclosed. Such apparatus is quite expensive and no positive way of unseating the check valve is disclosed. Such prior art devices are relatively impractical to implement and quite costly. In my copending U.S. application No. 688,029 filed concurrently herewith, I disclose a gas release probe for traveling-barrel type pumps for curing gas lock therein. However, traveling-plunger-type oil wells cannot use a gas release probe for practical reasons.
There is thus a need for eliminating gas lock in traveling plunger-type oil well pumps in an efficient and inexpensive manner.